Can computer‐assisted implant surgery improve clinical outcomes and reduce the frequency and intensity of complications in implant dentistry? A critical review

Abstract Computer‐assisted implant surgery (CAIS), either static or dynamic, is well documented to significantly improve the accuracy of implant placement. Whether the increased accuracy leads to a corresponding improvement in clinical outcomes has not yet been systematically investigated. The aim of this critical review was to investigate whether the use of CAIS can lead to reduction of complications as well as improved clinical and patient‐reported outcomes (PROs) when compared with conventional freehand implant surgery. A comprehensive online search was conducted to identify studies where implants were installed with static computer‐assisted implant surgery (s‐CAIS)or dynamic computer‐assisted implant surgery(d‐CAIS) or combinations of the two, either compared with conventional free‐hand implant placement or not. Seventy‐seven studies were finally included in qualitative analysis, while data from three studies assessing postsurgical pain were suitable for a meta‐analysis. Only a small number of the available studies were comparative. The current evidence does not suggest any difference with regard to intraoperative complications, immediate postsurgical healing, osseointegration success, and survival of implants placed with CAIS or freehand protocols. Intraoperative and early healing events as reported by patients in randomized clinical trials (RCTs) did not differ significantly between CAIS used with flap elevation and conventional implant placement. There is limited evidence that increased accuracy of placement with CAIS is correlated with superior esthetic outcomes. Use of CAIS does not significantly reduce the length of surgeries in cases of single implants and partially edentulous patients, although there appears to be a more favorable impact in fully edentulous patients. Although CAIS alone does not seem to improve healing and the clinical and PRO, to the extent that it can increase the utilization of flapless surgery and predictability of immediacy protocols, its use may indirectly lead to substantial improvements in all of the above parameters.


| INTRODUC TI ON
Computer-assisted implant surgery (CAIS) includes two major technological pathways, typically distinguished as static and dynamic Computer-assisted implant surgery (d-CAIS) or real-time navigation.
Static Computer-assisted implant surgery (S-CAIS) technology utilizes a surgical guide for guiding the osteotomy and implant installation, while the d-CAIS system guides the surgeon during osteotomy and implant placement through real-time imaging by means of optical tracking devices. Both systems are currently widely used and have been well documented to help surgeons achieve significantly higher accuracy of implant placement than conventional freehand surgery. Several recent systematic reviews and meta-analyses have shown superior outcomes in terms of accuracy for both static 1 as well as d-CAIS. 2,3 Accuracy of implant placement, however, is not the end purpose in itself. Instead, by offering superior accuracy, the endpoint of CAIS is to facilitate superior clinical outcomes, by reducing failures, complications, and adverse effects. There are many ways that increased accuracy is expected to influence clinical outcomes. Some authors have suggested that CAIS could reduce intraoperative complications by helping the surgeon avoid damaging sensitive anatomic structures such as the mandibular nerve and the sinus, as well as avoid proximity to roots of neighboring teeth. 4 Some have suggested CAIS could reduce the invasiveness, complexity, and duration of surgical interventions, while others have reported increasing patients' satisfaction and acceptance. 5 Finally, as this technology aims to empower the proper prosthetic-driven implant placement, it could potentially impact the long-term outcomes of implant therapy by allowing implant placement in the optimal position and angulation for prosthetic designs that could promote sustainable esthetic outcomes and health of the peri-implant tissue. 6,7 Optimal positioning of the implants may also reduce the cost of reconstruction, by allowing the use of stock abutments and minimizing the need for expensive customized solutions. Initial research on CAIS and consequent systematic reviews have primarily focused on reporting accuracy, although some authors acknowledge that survival rates, complications, patient-centered outcomes, and socioeconomic benefits are essential variables that cannot be ignored. 2 As these technologies are increasingly applied, assessing overall effectiveness and efficiency is critical to identify the potential and limitations of such systems, as well as help clinicians to make evidence-based decisions.

| Aims
1. Reduction of the frequency and extent of complications (intraoperative, postoperative, and medium/long term).
The secondary aims were to report the influence of CAIS on: 1. Clinical outcomes related to complications (plaque index, bleeding on probing (BOP), probing depth, keratinized mucosa, marginal bone loss (MBL), esthetic outcomes, duration of surgery).
2. Clinical outcomes related to the overall efficiency of CAIS (duration of the surgery, experience, and training of the operator).

| Methodology
A comprehensive online search was conducted in PubMed aiming to identify clinical trials in the last 10 years, where implants were installed with static or dynamic CAIS or combinations of the two, either compared with conventional free-hand implant placement or not. The electronic database PubMed was searched in February 2022 for articles in English with a limit of 10 years using the search query: {"Computer assisted implant surgery" OR "Computer aided implant Surgery" OR "guided implant Surgery" OR "implant navigation" OR "static guided" OR "dynamic guided"} AND Dental. In addition, a manual search was conducted on the reference lists of four recent systematic reviews and meta-analyses. 1-3

| Qualitative data synthesis and quantitative/ statistical analysis
In most cases, the heterogeneity of the data allowed only collective qualitative analysis. In the case of postsurgical PROs of pain originating from the first week of healing, a meta-analysis was conducted on three studies. 8,9,43 The meta-analysis was conducted using the software RevMan version 5.4 (Review Manager, the Cochrane Collaboration, 2020). Mean and standard deviation (SD) of patient-reporting pain scores at the designated time points derived from the selected articles were used as quantitative data, comparing the severity of pain between different types of surgery (static and d-CAIS data compiled vs freehand placement (FH), s-CAIS only vs FH). Thus, the standardized mean difference was applied to identify the magnitude of the effect and calculated 95% confidence interval. Then the random effect model was used for analysis. The heterogeneity across the studies was assessed by Chi-squared and I 2 tests. Forest plots were constructed to represent the results of meta-analysis of the included studies. A P value of less than .05 was judged to have statistical difference. Data were extracted and assessed by 77 studies (Table 1 and Figure 1).

Primary stability and related outcomes
Presence/absence of clinical primary stability. Four studies reported outcomes related to the implant primary stability, none of which compared outcomes between CAIS and FH. One comparative RCT by Ko et al 12 assessed clinical stability between immediate loading and delayed loading protocol with s-CAIS and reported that seven out of 93 implants (7.53%) (five maxilla/two mandible) in four out of 36 patients had insufficient implant stability in the immediate loading group. In other prospective and retrospective studies, an absence of clinical stability after placement with s-CAIS varied from 1.8% to 3.84% 10,11,13 (Table 2).
Quantitative measures of primary stability. Eleven studies assessed or reported primary stability after implant placement utilizing diverse outcomes measures, including insertion torque value (ITV), reverse torque (RT), and resonance frequency analysis (RFA) ( Table 3). Five of these studies were comparative, two RCTs comparing static computerassisted with freehand implant surgery and two RCTs comparing two different s-CAIS protocols. Smitkarn et al, 19 in an RCT, found statistically significantly higher implant stability quotient (ISQ) value in implants inserted freehand (bucco-lingual 72 ± 9, mesio-distal 72 ± 11) than with s-CAIS (bucco-lingual 63.5 ± 12, mesio-distal 65 ± 12). The same study found statistically significantly better ITV in implants inserted by freehand (35 ± 11 Ncm) than with s-CAIS (22.5 ± 20 Ncm  showing an optimal fit but only sufficient stability, and one supplemented by a simultaneous bone augmentation procedure after a dehiscence was detected.
With regard to implants placed with d-CAIS, one study 24 reported 100% survival after an average 1.5-year follow-up.

Peri-implant tissue conditions and related outcomes: mucositis/ peri-implantitis
The diagnosis of peri-implant mucositis/peri-implantitis is reported in four studies, none of which, however, provided detailed case definitions (Table 5). At 1-year follow-up, the prevalence of peri-implantitis for CAIS-placed implants varied from 0% 36 to 1.8%. 13 In the only comparative RCT, Almahrous et al 36

| Secondary clinical outcomes that can be related to complications and pathology
Plaque index, bleeding on probing, probing depth Assessment of plaque, bleeding, and/or probing depths around implants placed conventionally or with CAIS are reported in four studies, one of which is comparative ( respectively, at site level (Table 6).

Keratinized mucosa
The presence of keratinized mucosa at implants placed with s-CAIS and conventional FH has been assessed in two comparative studies (

Marginal bone loss
Changes in marginal bone level around implants placed conventionally or with CAIS have been reported in six studies (

Esthetic outcomes
Esthetic outcomes were assessed in three studies, none of which was Table 6 comparative. Fürhauser et al, 6 in a retrospective study, Moreover, the use of static or d-CAIS does not appear to lead to any different outcomes with regard to the morphology or inflammatory status of the peri-implant tissue, at least in the short to medium term.

| PROs and PRE of CAIS compared with conventional placement
Ten studies assessed PROs or PRE as primary or secondary outcomes (   assessing the same outcomes did not attempt statistical analysis. 16 The four above-mentioned studies qualify for a meta-analysis with regard to the outcomes of pain and swelling, thus the original raw data were requested from the respective authors. Data from three RCTs 8,9,43 were made available and were included in the meta-analysis conducted for pain and swelling during the first week after surgery (Figures 2 and 3). The meta-analysis confirmed the trend favoring CAIS, which did not, however, reach statistical significant difference (Figures 2 and 3). All studies that followed daily outcomes using a VAS showed a similar pattern of reduction in the intensity of the symptoms (Figures 4 and 5). Pain reached a peak at 6 hours 8,16 or on the first day, 9,43 painkiller consumption on the first day, 8,9 and swelling on the second day after surgery. 8,9,16,43 It should be noted that all five previously mentioned studies uti-   39 It is therefore reasonable to assume that the use of CAIS could indirectly contribute towards improving patient-reported healing outcomes, to the extent that it can facilitate and empower wider use of flapless surgery ( Figure 6).

F I G U R E 7
Overview of the principle characteristics of the static computer-assisted implant surgery (CAIS) systems utilized in studies analyzed in this review. Implants were placed with diverse combinations of planning software, surgical guide design, and manufacturing techniques, as well as guided surgery drills and sequences. To this diversity one can add the potential influence of different hardware and algorithms of cone beam computed tomography, intra-oral scanners, and hybrid digital-analog protocols D-CAIS has rarely been reported to have complications of a technical nature, but technical issues such as "loss of connection" between the sensors and the camera have been reported to be a nuisance, while system specifications, such as frame renewal rate, are indicated to significantly influence the duration of surgeries ( Figure 8). Although not as wide as with s-CAIS, high diversity exists within d-CAIS software and hardware, which can potentially influence performance and clinical outcomes. At the same time, d-CAIS is reported to be "operator sensitive" with a clinical study suggesting optimal results to be achieved only after treating at least 20 cases. 50 The findings of this review should be seen under the limitations of the available literature, as well as those of the current review, which was limited to the last 10 years, as the evolution of protocols might hamper comparisons with outcomes from older studies.
Nevertheless, some important older studies might still be relevant, and were therefore used in the discussion of the results where it was deemed appropriate.